1. Field of the Invention
The present invention relates to a coding apparatus and a coding method, and more particularly, to a coding apparatus and a coding method capable of executing a coding operation at higher speed.
2. Description of the Related Art
JPEG (Joint Photographic Experts Group) 2000, which was standardized in 2000 by ISO/IEC (International Organization for Standardization/International Electrotechnical Commission), is expected to be a technique replacing JPEG in that JPEG 2000 has numerous functions such as a high compression ratio, lossy and lossless compression correspondence, scalability (resolution, image quality, and the like), and error-resistance.
In 2004, JPEG 2000 Part-1 was selected as a standard codec by Digital Cinema Initiative (DCI) of a digital cinema. Accordingly, image photographing, image editing, and image delivery of digital cinema can all be standardized by JPEG 2000.
Conserving an original form of a medical image, a satellite image, or the like is necessary. In recent years, there are numerous single-lens reflex digital cameras capable of storing RAW data or RGB data acquired from an image sensor of CCD (Charge Coupled Device) or CMOS (Complementary Metal Oxide Semiconductor) in a memory card in a non-compression state.
However, when a master image is not compressed, an advantage is obtained in that data loss of an image scarcely occurs. However, there is a disadvantage in that the size of data is considerably increased. Therefore, in future, the necessity for compression and decompression by lossless compression of JPEG 2000 in usages, where image quality is important, other than digital cinema, will increase.
Japanese Patent No. 3906630 discloses an image coding apparatus that includes both a fixed point type wavelet transformer and an integer type wavelet transformer and is capable of executing both reversible transformation and irreversible transformation. Therefore, in this image coding apparatus, a degree of freedom of selecting image quality or compression ratio is improved.
In JPEG 2000, however, a problem may arise in that calculation load is considerably increased in comparison to JPEG. In particular, it may take an enormous amount of time to execute lossless compression since all coefficient data have to be compressed without loss.
In the coding technique of JPEG 2000, a first large calculation load is an entropy coding unit called EBCOT (Embedded Block Coding with Optimized Truncation). The entropy coding unit uses a technique of executing arithmetic coding while modeling binary data developed in a bit plane in one pixel unit. Therefore, since there is “dependency” that the result of a high bit plane influences the result of a low bit plane upon sequentially executing the processes, it is difficult to execute a parallel operation in the code block. For this reason, in a case of coding or lossless compression of an image with a large resolution, whatever the method, processing the calculation load of JPEG 2000, in particular, realization of the high speed EBCOT, is key.
It is desirable to provide a technique capable of executing a coding operation at higher speed.